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[SWMU B-31]

Known: Approximately 650 feet of active sanitary sewer pipe (8-inch vitrified clay) east of Building 90 was reportedly bedded in sand containing lead shot which was generated at the Building 90 test range. Three geophysical anomalies not associated with waste management practices were observed during geophysical survey activities on 11 March 1996.

Previous Investigations: In March 1996, a geophysical survey was conducted at the site. Three geophysical anomalies not associated with waste management practices were observed.

Three surface soil samples were collected on 12 March 1996 and analyzed by ITS Laboratory for explosives and metals. In addition, three soil borings were completed and six soil samples were collected (two samples from each boring) on 29 and 30 August 1996. These subsurface soil samples were analyzed by ITS Laboratory for explosives and metals.

In July 1997, efforts to remove the sand and projectile material were conducted. Since the specific location of this material was not known, test pits were dug in an effort to find it. A total of seven test pits were dug, but no sand and projectile material was found. One soil sample was collected from the bedding of each pit. Since the March 1996 data indicated that copper, lead, and zinc results exceeded background, the pit bottom samples were analyzed by ITS Laboratory for copper, lead, and zinc. Since the pipe is an active sanitary sewer line, the pits were backfilled immediately after sample collection.

Planned Rework: Replace previous analytical chemistry data generated by ITS laboratory. Since observations of the excavation material within the area in question indicates that there is no waste material in the pipe bedding, Parsons ES proposes that the rework sampling be focused on confirming this finding with soil boring analytical results. As noted above, March 1996 ITS results indicated that copper, lead, and zinc levels slightly exceeded background concentrations. Since the background evaluation will be redone as part of the rework, it is possible that rework soil boring results from B-31 will be found to not exceed background. To accomplish the replacement of analytical chemistry data from ITS, Parsons ES proposes three soil borings located as close as possible to the suspected pipe bedding material. These borings will be named RW-B31-SB1, RW-B31-SB2, and RW-B31-SB3. Three surface soil samples and two samples from each boring (trench bottom and total boring depth) will be analyzed for VOCs, metals and explosives.

Parsons ES proposes that pit bottom samples collected at SWMU B-31 not be repeated. Since this pipe is an active sanitary sewer line, excavation of pits where no waste material was found is not considered worth the risk of pipe damage. If soil borings are placed as close as possible to the pipe, a sample can be collected from each boring at a depth representative of the pit bottom.

Rationale for Analytical Program: SWMU B-31 consists of pipe bedding material (sand and projectiles) from the Building 90 test range. Therefore, chemicals of potential concern include VOCs, metals and explosives. Metals (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel and zinc) are included due to the metallic nature of the waste. Ammunition may include explosives residue therefore, an analysis for explosives will be conducted. VOCs analysis is included in the analytical program to detect typical contaminants associated with a disposal area. SVOCs are not included at this site since no evidence of waste burning has been found.

Resampling Activities: The following field activities will be performed to gather data for TNRCC closure submittal of SWMU B-31:

1. The boring logs from the original drilling of SB1, SB2, and SB3 will be copied and reviewed by the supervising geologist prior to beginning any rework at SWMU B-31. In particular, the geologist will review the PID readings and recovery volumes obtained from the existing boring.

2. Field locate previous sample locations (collected in 1996).

3. Complete three soil borings in the approximate locations of the first set of soil borings, completed in 1996. Boring and surface soil sample locations are shown in Figure B31-1. The rework soil samples will be collected from each boring from the same depth intervals as the first set of surface and subsurface soil samples. The total depth of each boring will be at approximately the same depth as the first set of soil borings (SB1 = 10 feet, SB2 = 10 feet, and SB3 = 10 feet BGL). Each rework sample will be analyzed for Voices, explosives and metals, as indicated in the table below. Metals include arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc. QA/QC samples will be collected as described in Section 2.4 of the FSP.

4. Boring logs for the rework soil borings will not be completed. Instead, the original boring logs created from the boring completed in 1996 will be available onsite during rework activities. Changes to the boring logs will be made if field personnel observe a difference in the rework boring from the original soil boring.

5. Water is not expected to be encountered in the borings at the site. However, if water is discovered in any of the soil borings, AFCEE and CSSA will be notified immediately. Completion of monitoring wells is not included in the scope of the rework as no wells were previously installed at the site.

6. Handle IDW as specified in the FSP.

7. Analytical results for the data quality rework samples will be reported in the Rework ITIR.

8. If the results of the above work indicate that the site can be closed under RRS1 without any further investigation and/or remediation, a technical/closure report will be prepared and submitted in accordance with TNRCC closure requirements. If the site does not meet RRS1 closure requirements, a technical report describing the results of the investigation and recommended additional investigation and/or remediation will be prepared under the RL17 SOW.

Notes: TBD = To be determined.
Metals = Arsenic (SW7060), barium (SW6010), cadmium (SW7131), chromium (SW6010), copper (SW6010), lead (SW7421), mercury (SW7470), nickel (SW6010), and zinc (SW6010).